The subject matter disclosed herein relates generally to methods of operating wind turbines and, more particularly, to a method of operating a wind turbine using forecasted wind speeds.
The output power generated by wind turbines is mainly dependant on the speed of wind incident on wind turbine rotors. Incident wind speed is also a determining factor for loads leading to fatigue and damage of the rotors. Since the wind field varies as a stochastic process, the rotor speed and pitch angles of rotor blades are adjusted by a feedback control to optimize the power output of a wind turbine while maintaining loads within acceptable limits. Wind turbines may also trip or stop power production to prevent excessive loads.
The performance of a wind turbine in terms of maximizing power output and minimizing loads depends on the location of sensors, actuators, and the feedback control algorithm for a controller. Sensors collect data about the incident wind speed either directly or indirectly via turbine measurements. The controller analyzes data collected by the sensors and typically commands the pitch angles of the rotor blades and the rotational speed of the rotor through actuators. In practice, the performance of a wind turbine is limited since the incident wind speed can change rapidly and the turbine can only react to such changes at a slow rate. Both the rotor speed and blade pitch angles can take a finite time to change to new set point values because of the large inertias of wind turbine components and limitations on actuator forces and torques. As a result, the wind turbine encounters higher loads and the energy captured by the wind turbine is suboptimal.
Extreme wind conditions such as sustained gusts can also lead to higher loads and possibly damage or cause shutdown events of the wind turbine. In the case of small temporary gusts, however, shutdown may be unnecessary due to the transient nature of gusts. However, the sensors on wind turbines may not differentiate short gusts from other extreme wind conditions. Shutdown of wind turbines during short gusts thus results in power loss that could have been avoided.
It would therefore be desirable to provide a wind turbine operation method that can anticipate and react to changes in wind conditions in a timely manner to mitigate loads and improve the efficiency of the wind turbine.